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Semester 1-ICPP > Action Potential (session 5) > Flashcards

Action Potential (session 5) Flashcards

1
Q

What does the action potential depend on?

A

Ionic gradients

Relative permeability of the membrane

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2
Q

What is the action potential?

A

Change in voltage across the membrane

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3
Q

True or false: the action potential is propagated with loss of amplitude

A

FALSE - there is no loss of amplitude

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4
Q

True or false: depolarisation to threshold initiates an action potential at the axon hillock

A

TRUE

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5
Q

What is the driving force?

A

Difference between membrane potential and equilibrium potential

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6
Q

Complete the sentence:

If the conductance (g) to any ion is increased, the membrane potential (Vm) will move ______ to the equilibrium potential for that ion.

A

Closer

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7
Q

What is the conductance of the membrane to a particular ion dependent on?

A

The number of channels for that ion that are open

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8
Q

True or false: sodium equilibrium potential dictates the generation of an action potential

A

TRUE

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9
Q

True or false: not many ions need to flow for an AP to be initiated

A

TRUE

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10
Q

What is capacitance?

A

Ability to store charge

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11
Q

True or false: the Na+/K+ ATPase pump is needed for repolarisation

A

FALSE

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12
Q

What do voltage-clamps allow?

A

Membrane currents to be measured at a set membrane potential

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13
Q

What is the absolute refractory period?

A

Nearly all Na+ channels are in their inactivated state and no matter how strong the stimulus is, no AP is initiated

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14
Q

What is the relative refractory period?

A

Na+ channels are recovering from inactivation, excitability returns towards normal as number of channels in the inactivated state decreases. If there is a strong stimulus, another AP may be initiated

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15
Q

How many alpha subunits does the functional channel of a voltage gated Na+ channel have?

A

One

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16
Q

How many alpha subunits does the functional channel of a voltage gated K+ channel have?

A

Four

17
Q

True or false: voltage gated K+ channel is 1/4 the size of a Na+ channel

A

TRUE - 4 subunits are needed to make a functional K+ channel

18
Q

True or false: channels open and close in a random manner

A

TRUE

19
Q

How do local anaesthetics work?

A

By blocking Na+ channels (no AP)

20
Q

Give an example of a local anaesthetic

A

Procaine

21
Q

In what order do local anaesthetics block axons?

A
  1. Small myelinated axons
  2. Unmyelinated axons
  3. Large myelinated axons
22
Q

Complete the sentence:

Injection of current into an axon will cause the resulting charge to spread along the axon and cause an _________ _____ ______ in the membrane potential.

A

Immediate local change

23
Q

What does membrane resistance depend on?

A

Number of ion channels open

24
Q

Complete the sentence:

The lower the resistance, the _____ ion channels are open.

A

More

25
Q

Complete the sentence:

A high capacitance leads to the voltage changing more ______ in response to current injection

A

Slowly

26
Q

Complete the sentence:

High resistance leads to a change in voltage spreading ________ along the axon

A

Further

27
Q

Complete the sentence:

The wider the axon, the ______ and _______ the conductance of the AP

A

Faster

Further

28
Q

Schwann cells are in which nervous system? And what is the equivalent in the other nervous system?

A

PNS

Oligodendrocytes

29
Q

Is there a high or low density of Na+ channels at the nodes of Ranvier?

A

High

30
Q

What is saltatory conduction?

A

Action potential ‘jumping’ from node to node, allowing a much faster conduction velocity

31
Q

True or false: AP occurs only at nodes

A

TRUE

32
Q

How does the myelin sheath improve conduction? (4)

A
  1. Large increase in membrane resistance (Rm)
  2. Large decrease in membrane capacitance (Cm)
  3. The above increase length constant
  4. Slight decrease in time constant
33
Q

Name some diseases that affect the conduction of the AP in the CNS and briefly describe which nerves they affect (2)

A
  1. Multiple sclerosis - affects all CNS nerves

2. Devic’s disease - optic and spinal cord nerves only

34
Q

Which diseases affect the conduction of APs in the PNS? (2)

A
  1. Landry-Guillain-Barre syndrome

2. Charcot-Marie-Tooth disease

35
Q

Diseases affecting the conduction of the AP result from the breakdown or damage of what?

A

The myelin sheath

36
Q

Complete the sentence:

In regions of demyelination, the density of the action current is reduced because of _________ and ___________ ________

A

Resistive

Capacitance shunting

Semester 1-ICPP (12 decks)

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